Field of the Invention
The present invention relates to an adapter device, an imaging apparatus, and an accessory.
Description of the Related Art
Conventionally, accessories such as interchangeable lenses and so forth (camera accessories) are known to be able, when mounted to an imaging apparatus such as a digital camera (hereinafter, referred to as a “camera”) or the like, to receive a supply of power from the camera and to enable communication of commands, data, and so forth between the accessory and the camera. It is known that multiple contacts (terminals) capable of electric connection, by coming into contact, are provided on both the camera and a mounting portion of the accessory, in order to enable the supply of power and the communication. There is also known a mounting system for mounting (coupling) the accessory to the camera employing so-called bayonet coupling, where mounts of both the camera and accessory are rotated relative to each other, and bayonet/mount claws provided on each apparatus engage with the claws provided on the other apparatus.
Combinations that corresponding to each other are decided beforehand for cameras and accessories employing a mounting system such as described above. For example, corresponding accessories (e.g., interchangeable lenses, etc.) differ depending on the length of the flange focal distance of the camera. In other words, there are accessories that are not compatible with the flange focal distance of a given camera.
In a case where an accessory that is not compatible with a camera is mounted, problems may occur. For example, in a case where an interchangeable lens that is not compatible with a camera having a certain flange focal distance is mounted thereto an optical image of a subject entering via the interchangeable lens cannot be focused on the image plane of the camera or the like. Accordingly, there is a need to restrict the connecting of cameras and accessories in combinations that are mutually incompatible. In particular, in a case where multiple accessories that are compatible with different cameras have mount diameters that are generally the same, it is difficult to judge from the external appearance of the cameras and accessories whether they are a compatible combination or not.
Japanese Patent Laid-Open No. 2005-70712 proposes a technology where a protrusion of a lens, that has the same flange focal distance but a short back focus, abuts a wall portion provided to a camera body, thereby preventing erroneous mounting of this lens to a camera body that cannot operate correctly with mounted lenses with short back focus.